(1) Field of the Invention
The present invention relates generally to systems for controlling electromagnetic radiation, and more particularly to an electromagnetic wave interface that may be utilized to capture electromagnetic radiation such as radio waves and transform the radiation by some desired means such as by absorbing the radiation completely for stealth purposes, reflecting the radiation with desired characteristics that alter the radiation in a desired manner, by transforming the radiation into digital data without analog receivers, and/or otherwise processing the radiation.
(2) Description of the Prior Art
Traditional antenna theory requires that as the capture area of an antenna becomes smaller, the Q increases, and the bandwidth narrows. Thus, according to traditional antenna theory it is impossible to provide a wide bandwidth antenna with a small capture area. Moreover, prior art broadband receiving systems are performance limited by the inability to realize sufficient spurious-free dynamic range (SFDR) in the analog portions of the receiving systems. Prior art broadband receiving systems may often be limited to about 60 db SFDR.
Prior art antennas are also limited as to the type of functions that are available. Generally, prior art antennas are dedicated to perform a certain function and are not suitable for other specific functions. For instance, a prior art antenna design may be utilized as a transceiver. However, a prior antenna design will not be useable for transceiver operation, and/or stealth operation as being electrically “black,” and/or altering radio wave electromagnetic radiation Doppler effects to produce a desired reflection which may indicate a body traveling at a different speed than it is, and/or for producing a radio reflection signature that may be different from the actual body producing the reflection.
The following U.S. patents describe various prior art systems that act in some way on electromagnetic radiation. Many of the disclosed structures are not broadband structures and several are limited to certain frequencies, such as sunlight, or other very specific functions not related to radio waveband electromagnetic radiation.
U.S. Pat. No. 3,836,967, issued Sep. 17, 1974, to R. W. Wright, discloses a structure for impeding the reflection of a beam of electromagnetic waves from the surface of an object and more particularly to a flexible, thin-wall structure which is suitable as a broadband absorber of microwave energy.
U.S. Pat. No. 4,582,111, issued Apr. 15, 1986, to R. D. Kuehn, discloses a substantially radiation absorbing layer of metal having a microstructured surface characterized by a plurality of randomly positioned discrete protuberances of varying heights and shapes, which protuberances have a height of not less than 20 nanometers nor more than 1500 nm, and the bases of which contact the bases of substantially all adjacent protuberances. The metal layer, which may be a coating on a variety of substrates, is useful as a radiation absorber (particularly solar). A method is disclosed for producing such layers.
U.S. Pat. No. 4,672,648, issued Jun. 9, 1987, to Mattson et al., discloses an off-focal radiation collimator which includes a plurality of radiation absorbing elements supported in spaced relationship with respect to one another in a housing such that each element is aligned along radii extending from the focal spot of a radiation source. The off-focal collimator is preferably disposed between the radiation source and a primary beam collimator. The off-focal collimator also acts as a radiation beam compensator. By varying the spatial density of the radiation absorbing elements by a function of location within the housing, the radiation beam can be shaped to any desired profile.
U.S. Pat. No. 4,942,402, issued Jul. 17, 1990, to Prewer et al., discloses an absorber for radiation of frequency of the order of 1 THz is formed of a body of cured silicone-based elastomer containing an inert, powdered siliceous filler. Both the elastomer and the filler are electrically insulating and the surface of the absorber that is exposed to the radiation is preferably profiled to enhance absorption of the radiation. The profiling preferably takes the form of an array of sharp-pointed pyramids having rectangular or triangular bases. A method of molding such absorbers is also disclosed.
U.S. Pat. No. 5,565,822, issued Oct. 15, 1996, to Gassmann et al., discloses a TEM waveguide arrangement such as are used in testing the electromagnetic compatibility of electronic devices in electromagnetic fields wherein a plate-shaped inner conductor is connected via electrically parallel-connected tubular resistors to an electrically conductive, spherical rear wall. This rear wall is electrically connected to an outer conductor and grounded. Radio-frequency absorbers are mounted on the rear wall for the purpose of absorbing TEM waves, the RF short-point absorbers adjacent to the tubular resistor being smaller than the remaining RF long-point absorbers, in order to reduce the capacitive influence of the tubular resistors. Identical tubular resistors are arranged perpendicular to the plane of the drawing of FIG. 1 in accordance with a current density distribution in such a way that they are more closely adjacent at the edge than in the middle of the inner conductor.
U.S. Pat. No. 5,710,564, issued Jan. 20, 1998, to Nimtz et al., discloses an electromagnetic wave measurement chamber wherein the sidewalls and the ceiling of the chamber are lined with contiguous pyramids. The pyramid vertices point into the chamber. The structure element has a frame formed by bars made of an electrically insulating glass fiber material and an outer skin. The outer skin is cut out of a surface resistance material web. The surface resistance material web is produced by continuously or almost continuously coating a mechanically flexible support web with an electroconductive layer made of a metallic material.
U.S. Pat. No. 6,295,032 B1, issued Sep. 25, 2001, to A. S. Podgorski, discloses electromagnetic radiating structures suitable for use as antennas or in electromagnetic field test facilities. An electromagnetic field test facility is a test enclosure used for observing the behavior of equipment in the presence of strong electromagnetic fields and for detecting radiation from the equipment. A broadband Gigahertz field electromagnetic test facility is also disclosed in which an array of horn antennas is used to illuminate a relatively large test area at high power densities, or to measure radiation from tested equipment in a frequency range extending from DC to hundreds of Gigahertz.
U.S. Patent Application Publication No. 2001/0003444 A1, published Jun. 14, 2001, to Mangenot et al., discloses a radiating source for transmitting and receiving, intended to be installed on board a satellite to define a radiation pattern in a terrestrial zone. The source is intended to be disposed in or near the focal plane of a reflector associated with other sources corresponding to other terrestrial zones. The source includes a plurality of radiating apertures, each of which has an efficiency at least equal to 70%, and feed means for feeding said radiating apertures. The radiating apertures and their feed means are such that the energy radiated by all of the radiating apertures is practically limited to the corresponding reflector, at least for transmission.
U.S. Patent Application Publication No. 2001/0033377 A1, published Oct. 25, 2001, to Welch et al., discloses systems for, and methods of controlling radial energy density profiles in, and/or cross-section dimensioning of electromagnetic beams in polarimeters, ellipsometers, reflectometers and spectrophotometers.
U.S. Patent Application Publication No. 2001/033207 A1, published Oct. 25, 2001, to Anderson et al., discloses phase shifting plasma electromagnetic waveguides and plasma electromagnetic coaxial waveguides, as well as plasma waveguide horn antennas, each of which can be reconfigurable, durable, stealth, and flexible are disclosed. Optionally, an energy modifying medium to reconfigure the waveguide such that electromagnetic waves of various wavelengths or speeds can be propagated directionally along the path can be used. Similarly, these waveguides may be modified into coaxial configurations.
U.S. Pat. No. 6,300,918 B1, issued Oct. 9, 2001, to Riddle et al., discloses a phased array antenna that includes a plurality of multiple spiral arm antenna elements. The antenna elements are hexagonal in shape and are aligned in a triangular lattice geometry, where the elements are arranged in rings around a common center element. The elements include at least two arms which terminate at opposite sides of the element. The ends of the arms of diagonally adjacent elements are positioned proximate to each other to provide inter-element coupling to increase the bandwidth of the antenna. The tight coupling of the antenna elements also reduces the RCS of the antenna.
U.S. Pat. No. 6,215,448 B1, issued Apr. 10, 2001, to DaSilva et al., discloses a selected length of antenna for a device under test which is placed within a conductive inner cylinder, forming an unterminated “input” coaxial transmission line. The inner cylinder is in turn within and coaxial with a conductive outer cylinder, forming an “output” transmission line. The inner cylinder is the center conductor of the output transmission line, and in a region extending beyond the extent of the antenna therein, conically tapers to being a normal center conductor of solid cross section. The outer cylinder matches this taper to maintain a constant characteristic impedance Z0 say, 50 ohms, for the output transmission line, which then delivers its output signal to a matched terminating load in measurement equipment via either a coaxial connector or an interconnecting length of auxiliary transmission line. These triaxially nested input and output transmission lines are supported at a driven end by an RF tight box that contains a mounting fixture to support the device under test in a fixed and appropriate relation to the triaxially nested input and output transmission lines, and that is lined with anechoic RF absorbing material.
U.S. Pat. No. 6,021,241, issued Feb. 1, 2000, to Bilbro et al., discloses an array of optical fiber bundles includes one or more diffractive elements positioned above gaps between adjacent bundles. Incident radiation produces mathematically determinative diffraction patterns on the respective input faces of the adjacent bundles. Radiation intensity values for areas between and along the abutting edges of adjacent optical fiber bundles can be determined using the diffraction patterns. These intensity values can be assigned to other pixels so that precise, seamless images can be reconstructed.
U.S. Pat. No. 6,285,495 B1, issued Sep. 4, 2001, to Baranov et al., discloses an optical element comprising a plurality of transparent layers comprising one or more passive layers and one or more active layers wherein said passive layers facilitate the transmission of electromagnetic radiation in a substantially unaltered form and the at least one active layers include an active material dispersed through the active layer and having the capacity to intercept electromagnetic radiation of at least one predetermined wavelength or range of wavelengths and redirect at least a portion of energy of the intercepted radiation into the interior of the optical element, said layers being in face to face relationship and being optically coupled to each other.
U.S. Pat. No. 6,329,955 B1, issued Dec. 11, 2001, to McLean et al., discloses a broadband antenna incorporating both electric and magnetic dipole radiators includes a tapered feed, such as a bow-tie feed, having a central feed point and first and second outer regions displaced from the central feed point. One or more conducting loop elements are connected between the outer regions of the tapered feed. Top loading capacitive elements extending from each of the outer regions may also be provided.
U.S. Pat. No. 6,297,774 B1, issued Oct. 2, 2001, to H. H. Chung, discloses a high performance phased array antenna system for receiving satellite communication signals, with a structural top layer formed as a perforated plate (or solid plate made of very low loss plastic material), a middle layer functioning as the single layer antenna aperture layer, preferably in the form of a single layer printed circuit board on which is formed an array of antenna elements and plurality of stripline feed network circuits, each combining in-phase outputs from several adjacent antenna elements, the bottom layer functioning as the ground plane for the antenna aperture layer and also including a single level waveguide combining network for combining in-phase outputs from stripline feed network circuits electromagnetically coupled to respective transition probe holes of the waveguide combining network. Each antenna element is preferably a dual polarization octagonal patch antenna element disposed on a common surface of the antenna aperture layer. Each feed network circuit is preferably in a form of an air-stripline feed network separated by a layer of air dielectric from the ground plane and preferably is on the same surface of the antenna aperture layer as the antenna elements. The single level waveguide combining network is preferably an integral structure including dual orthogonal polarization waveguide sections and dual orthogonal polarization ports. The dual orthogonal polarization waveguide sections lay in the same plane and preferably are asymmetrically disposed on either side of a common wall, with each containing a branched cavity symmetrically disposed about a respective centerline.
U.S. Pat. No. 6,292,140 B1, issued Sep. 18, 2001, to D. P. Osterman, discloses a novel antenna which is useful in the manufacture of a bolometer integrated on a silicon chip. An opening in the silicon chip is spanned by two separate thermally, isolated structures. A thin-film antenna, comprising two parts, is located on the structures, with one antenna part on each structure. Radiation received in the larger of the two antenna parts is coupled electromagnetically into the smaller part, where it causes a current to flow. The current is dissipated as heat. A thin-film thermometer measures the temperature rise of the smaller antenna part, due to the dissipated heat. The bolometer achieves improved performance in comparison to previous bolometer designs because the radiation is dissipated in a part of the antenna only, and the bolometer is free from impedance-matching constraints of other designs.
U.S. Pat. No. 5,926,147, issued Jul. 20, 1999, Sehm et al., discloses an antenna design that includes a plurality of radiating elements which radiate electro-magnetic energy, and feeders which feed the electromagnetic energy to the radiating elements. The feeders have a supply network substantially at the same level in the antenna thickness direction. In order to achieve a small antenna with adequate properties for radio link usage, the radiating elements are arranged next to the supply network in the thickness direction and include box horn antennas which have a step, characteristic of a box horn, in the plane of the magnetic field.
U.S. Pat. No. 5,539,421, issued Jul. 23, 1996, to S. Hong, discloses a planar antenna, for use in satellite communication that is intended to provide higher aperture efficiency, improved circular polarization and increased production tolerability. The antenna comprises a waveguide and an array of M×N helical antenna elements, wherein M and N are integers. The waveguide includes a primary feeder waveguide and a set of M secondary feeding waveguides, wherein each of the M secondary feeding waveguides is provided with N helical antenna elements, each of the secondary feeding waveguides is coupled to the primary feeder waveguide through an aperture so that received signals from N helical antenna elements in each of the second feeding waveguides are combined at the primary feeder waveguide.
Prior art systems do not provide a broadband antenna with a small capture area. Moreover, the prior art typically does not provide a basic structure that can perform a variety of widely divergent functions to radio wave electromagnetic radiation such as, for instance, communication and radar. Thus, it would be desirable to provide a structure that permits complete absorption of electromagnetic radiation such as radar so as to eliminate reflections for stealth purposes and/or which may otherwise be utilized to more completely absorb radiation to act as an receiving antenna, and/or may be utilized as a broadcasting antenna, and/or as a modulating system to provide the receiving radar with inaccurate appearance of the return signal related to speed and shape, and/or other purposes as discussed in more detail hereinafter. Consequently, those skilled in the art will appreciate the present invention that addresses the above and other problems.